During the past several years we have defined a novel pathway of immunoregulation effected by CD8+ T cells which recognize and control the outgrowth of autoreactive CD4+ T cells expressing certain T cell receptor (TCR) Vbeta molecules (reviewed in Jiang, H., and L. Chess. Annu. Rev. hnmunol. 18:185, 2000.). Interestingly, these TCR Vbeta specific regulatory CD8+ T cells have recently been shown to control the autoimmune CD4+ TCR Vbeta repertoire at a clonal level during the development of autoimmunity in mice. Moreover, the regulatory CD8+ T cells also cognitively discriminate between TH1 and TH2 cells and in vivo control the balance of TH1 and TH2 autoreactive T cells that emerge following autoantigen triggering. The precise specificity of these regulatory CD8+ T cells is not known, however, in mice they are restricted by MHC class Ib molecule, Qa-1. In this proposal, which is interactive with the Jiang project and relies on clinical material in the Herold anti-CD3 project we will test the hypothesis that these CD8+ regulatory T cells control the emergence of autoreactive CD4+ T cells in type I human diabetes (Dr. Chess, PI) by specifically deleting or inactivating unique clones of autoreactive CD4+ TH1 cells. In man, we have developed evidence that TCR Vbeta specific CD8+ T cells can be identified and cloned from normal individuals. Interestingly, these CD8+ T cells can be restricted by HLA-E, the human homologue of Qa-1. We also have shown that these CD8+ T regulatory cells emerge during the course of human multiple sclerosis which are capable of specifically down regulating autoantigen (MBP) specific CD4+ T cells in a T cell receptor (TCR) Vbeta specific manner in vitro. In this project we will extend these studies to type I diabetes (T1D) and determine if regulatory CD8+ T cells regulate diabetic activity and control the outgrowth of the autoreactive T cell repertoire and the TH phenotype in human T1D. Initially, we will concentrate on the control of CD4+ T cells reactive with putative diabetes associated antigens GAD and later extend this analysis to other islet cell specific or other T1D antigens including insulin and HSP. Moreover, because recent evidence suggest that certain HLA-E genotypes predict disease susceptibility to human T1D, we plan to identify known polymorphisms of HLA-E alleles in the T1D patients and correlate HLA-E polymorphic variations with the capacity to generate CD8+ regulatory cells and with clinical course.